Sublimable film formation composition and method for producing substrate

The present invention relates to a sublimable film formation composition and a method for producing a substrate.

Various developments have been made regarding production processes for substrates on which an uneven structure is formed. As a technique of this kind, for example, the technique described in Patent Document 1 is known.

Patent Document 1 describes a substrate drying method for drying a substrate by removing a liquid on the substrate on which an uneven pattern is formed on a surface, the method being provided with a sublimable substance filling step of supplying a sublimable substance solution to the substrate to fill the solution in recessed portions of the pattern, a solvent drying step of drying the solvent in the solution and filling the inside of the recessed portions of the pattern with the sublimable substance in a solid state, and a sublimable substance removal step of removing the sublimable substance from the substrate by heating the substrate to a temperature higher than the sublimation temperature of the sublimable substance (claimof Patent Document 1).

However, as a result of investigation by the present inventors, it was found that, in the solution of the sublimable substance described in Patent Document 1 described above, there is room for improvement in terms of the production stability of the substrate.

As a result of further investigation by the present inventors, it was found that even in a case where a solution including a sublimable substance and a solvent is used, there is a concern that a large number of pattern collapses may occur in the uneven structure on the substrate.

The present inventors carried out further intensive research based on such findings and found that, in a sublimable film formation composition including a sublimable substance and a solvent, by appropriately selecting a solvent in which the solubility of the sublimable substance is comparatively high and with a comparatively high volatility, or by appropriately combining two or more solvents, it is possible to suppress the occurrence of pattern collapse and to improve the production stability of the substrate, thereby completing the present invention.

According to the present invention, there is provided a sublimable film formation composition including

According to the present invention, there is provided a sublimable film formation composition including

In addition, according to the present invention, there is provided a method for producing a substrate, the method including

According to the present invention, there is provided a sublimable film formation composition with excellent substrate production stability and a method for producing a substrate.

A description will be given of the sublimable film formation composition of the present embodiment.

The sublimable film formation composition of the first embodiment includes a sublimable substance and the solvent A1 in which a saturation solubility of the sublimable substance is more than 10% by mass and a boiling point is lower by 5° C. or more than a boiling point of the sublimable substance at 1 atm.

The sublimable film formation composition of the second embodiment includes a sublimable substance, the solvent A2 in which a saturation solubility of the sublimable substance is more than 10% by mass, and the solvent B2 in which a content in the sublimable film formation composition is greater than a content of the solvent A2 and a boiling point is less than a boiling point of the sublimable substance at 1 atm and less than a boiling point of the solvent A2.

It is possible to suitably use the sublimable film formation compositions of the present embodiment in a production process of a substrate having an uneven structure on a surface and to suppress pattern collapse in the uneven structure of the substrate.

are cross-sectional views of steps showing an example of steps for producing a substrate using a sublimable film formation composition.

shows a step of supplying a sublimable film formation compositionto the surface of a substrateand filling the sublimable film formation compositionin a recessed portionin an uneven structure;shows a step of causing the sublimable film formation compositionto coagulate to form a sublimable film; andshows a step of removing the sublimable filmby sublimating the sublimable substance.

A description will be given of an example of producing a semiconductor chip. In this production process, a fine uneven pattern is formed on the substrate (wafer) surface through film deposition, lithography, etching, and the like, then a wet treatment such as a cleaning step using water or organic solvents is performed to make the wafer surface clean, and a drying step is also performed to remove liquids such as cleaning liquids and rinsing liquids attached to the wafer by the wet treatment.

It is known that, during the drying step, semiconductor substrates having fine uneven patterns are prone to deformation and collapse of the uneven patterns.

In order to dry a substrate on which an uneven pattern is formed using a sublimable substance, generally, a step is performed in which a residual liquid remaining in the uneven pattern is replaced by a treatment liquid including the sublimable substance.

According to the findings of the present inventors, it was found that, in a sublimable film formation composition including a sublimable substance and a solvent, by appropriately selecting a solvent in which the solubility of the sublimable substance is comparatively high and with a comparatively high volatility, or by appropriately combining two or more solvents, when the sublimable film formation composition is used in a production process for a substrate having an uneven structure, it is possible to suppress the occurrence of pattern collapse in the uneven structure of the substrate.

As shown in the first embodiment, the solvent A1 in which the sublimable substance solubility is moderate and which has moderate volatility may be adopted and, as shown in the second embodiment, the solvent A2 in which the sublimable film solubility is moderate and the solvent B2 having moderate volatility may be used together.

Although the detailed mechanism thereof is not clear, it is considered that, by using highly volatile solvents (the solvent A1 or the solvent B2)), which are more volatile than the sublimable substance, the film forming ability is high, while by using high solubility solvents (the solvent A1 or the solvent A2), in which the solubility of the sublimable substance is comparatively high, it is possible to suppress the excessive occurrence of precipitation of the sublimable substance at an early stage, thus, it is possible to suppress pattern collapse caused by the precipitated sublimable substances at an early stage.

In addition, in the technical field of substrates having a fine uneven structure, such as semiconductor wafers, pattern collapse is generally known as a state in which a pattern in a predetermined range collapses in a random direction, that is, referring to a planar collapse.

However, it was found that, in the types of pattern collapse, there is striated collapse, which is different from planar collapse.

Striated collapse basically refers to a state in which the pattern collapses continuously in a predetermined direction. Striated collapse may also be generated around regions where there is no predetermined pattern collapse. Even when it is possible to control the planar collapse and pattern collapse rate, there is a concern that striated collapse may occur.

According to the findings of the present inventors, it was found that, by using the solvent A1 or the solvent A2, which have an even higher sublimable substance solubility, and/or by using a sublimable substance with a comparatively low coagulation heat, it is possible to suppress striated collapse within pattern collapse.

Although the detailed mechanism thereof is not clear, it is considered that striated collapse is caused by distortion at the crystal grain boundaries of the sublimable film. For this reason, it is considered that by using solvents with high solubility, it is possible to suppress partial crystallization starting from the portion where the sublimable substance precipitated at an early stage, or, by using sublimable substances with a low coagulation heat to reduce the crystallinity, it is possible to suppress the striated collapse described above.

It is possible to suitably use the sublimable film formation composition of the present embodiment in a composition for drying uneven patterns used in a step of drying the uneven structure in the steps of producing a substrate having an uneven structure.

The sublimable substance may be a substance in which the entire film disappears due to a predetermined heat treatment, or may be a substance that disappears when the film is left at 23° C. under 1 atm. In the method for producing a substrate, the sublimable film is not a permanent film that remains permanently on the substrate, but is used as a sacrificial film to be removed in subsequent steps. Accordingly, it is possible to use the sublimable film formation composition as a composition for forming a sublimable sacrificial film.

A detailed description will be given below of the sublimable film formation composition of the present embodiment.

(Sublimable Substance)

The sublimable film formation composition includes one or two or more sublimable substances.

In the present specification, sublimable substance refers to a substance having a vapor pressure in a solid state.

In principle, it is possible to use the sublimable substance as long as the substance is solid and has a vapor pressure at a specific temperature.

The lower limit of the coagulation point of the sublimable substance is, for example, 5° C. or higher, preferably 20° C. or higher, and more preferably 50° C. or higher under 1 atm. Due to this, in a case of being applied to the method for producing a substrate, it is unnecessary to treat the sublimable substance at an extremely low temperature for coagulation and the production stability of the semiconductor substrate is increased.

On the other hand, the upper limit of the coagulation point of the sublimable substance is, for example, 220° C. or lower, preferably 200° C. or lower, and more preferably 180° C. or lower under 1 atm. Due to this, in a case of being applied to the method for producing a substrate, it is unnecessary to treat the sublimable substance at an extremely high temperature for sublimation and the production stability of the semiconductor substrate is increased.

The lower limit of the coagulation heat of the sublimable substance is not particularly limited, but may be, for example, 1 J/g or more, preferably 5 J/g or more, and more preferably 10 J/g or more.

On the other hand, the upper limit of the coagulation heat of the sublimable substance is 200 J/g or less, preferably 100 J/g or less, and more preferably 50 J/g or less. Due to this, it is possible to suppress the occurrence of striated collapse.

The sublimable substance may be formed such that non-volatile substances becoming residues after sublimation are substantially not included. It is possible to remove non-volatile substances from the sublimable substance by separation methods such as sublimation refining or distillation. Substantially not included means 1% by mass or less in 100% by mass of the sublimable substance, preferably 0.5% by mass or less, or that a case of unavoidable mixing in may be acceptable.

The lower limit of the boiling point of the sublimable substance is, for example, 60° C. or higher, preferably 100° C. or higher, and more preferably 110° C. or higher under 1 atm. Due to this, it is possible to stably form sublimable films including sublimable substances.

On the other hand, the upper limit of the boiling point of the sublimable substance is, for example, 300° C. or lower, preferably 280° C. or lower, and more preferably 250° C. or lower under 1 atm. Due to this, refining of the sublimable substance is easy. In addition, in a normal temperature and normal pressure process, the sublimation of the sublimable substance is easy and the production efficiency is increased.

As the boiling point or sublimation point of a sublimable substance including a plurality of substances, the boiling point or sublimation point of the component with the highest content (% by mass) among the components included in the sublimable substance is adopted (however, in a case where there are two or more components with the highest content, the boiling point or sublimation point which is the highest temperature is adopted). For the boiling point of sublimable substances, the initial boiling point as defined in JIS K 2254:2018 (ISO 3405) is adopted. In cases where the sublimation point is typically used for a substance, the sublimation point is used.

In addition, for the coagulation point of the sublimable substance, the coagulation start temperature determined using DSC under a condition of −10° C./min is adopted. As the coagulation point of a sublimable substance including a plurality of substances, the coagulation point of the component with the highest content (% by mass) among the components included in the sublimable substance is adopted (however, in a case where there are two or more components with the highest content, the coagulation point which is the higher temperature is adopted).

The temperature range at which the sublimable substance is solid and has a vapor pressure (also referred to below as “sublimation temperature range”) may, for example, be 10° C. or higher. Due to this, even when used in an environment of 20° C. to 25° C., which is a typical room temperature in a clean room, it is possible to coagulate the sublimable substance by cooling due to the heat of vaporization of the solvent in the sublimable film formation composition.

In addition, when the sublimation temperature range is in a range of 20° C. to 25° C., sublimation acceleration treatments such as heating and depressurization are not necessary and it is possible to sublimate the sublimable substances comparatively easily and to remove the sublimable film while adopting current substrate production process conditions as they are.

The vapor pressure when defining the sublimation temperature range is, for example, 10 Pa or more and preferably 50 Pa or more.

In the present specification, “to” indicates that the upper limit value and lower limit value are included, unless otherwise expressly stated.

Sublimable substances are not limited as long as application is possible to substrate materials such as semiconductors and examples thereof include non-halogenated sublimable substances S1 with a comparatively low coagulation heat, non-halogenated sublimable substances S2 with a comparatively high coagulation heat, sublimable substances S3 where the difference between the coagulation point and boiling point is comparatively small, halogen-containing sublimable substances S4 including halogen elements, and the like. The above may be used alone or in a combination of two or more.

The coagulation heat of the non-halogenated sublimable substance S1 is preferably 50 J/g or less and more preferably 40 J/g or less. For S1, the difference between the coagulation point and the boiling point tends to be comparatively large, thus, distillation and refining as a liquid are possible. The use of S1 makes it possible to prevent the occurrence of striated collapse.